[Distributed] Set stdin to devnull before closing it (#44881)
* [Distributed] Set stdin to devnull before closing it
Distributed closes and destroys stdin, but some tests attempted to
explicitly use it, leading to test problems. We previously interpreted
this as passing devnull, but this is better to be explicit.
* Revert "Testsystem: for now, move the REPL tests to node 1 (#44880)"
This reverts commit 7401e92a930ab51ff74e67a27152df5c2acd459b.
